VisualDx - Diagnosis Details - Child Rash: Pediculosis Capitis

132.0 – Pediculus capitis [head louse]

Pediculosis capitis, also known as head lice, is caused by Pediculous humanus capitis (head lice). Pediculosis typically affects children between ages 3–11 of all socioeconomic groups. Transmission is by close contact (direct head-to-head contact) and fomites (eg, on clothes, brushes, linens, combs, hats, etc). Lice live approximately 30 days on the host and 1–3 days off the host. Eggs (nits) hatch within 7–10 days.

Resistance to permethrin, pyrethrins, malathion, and lindane has been documented.

Look For

Lice and nits in the scalp and hair.

The adult lice are small wingless ectoparasites. They are 1–3 mm long with elongated bodies and 3 pairs of claw-like legs.

Nits appear as 0.5–1 mm grey-white specks that are firmly attached to individual hair shafts. Microscopy will reveal an oblong structure attached to the hair at an acute angle with a lobular breathing apparatus at its superior end.

Cervical and occipital lymphadenopathy may occur as a result of secondary infection.

Diagnostic Pearls

Pyodermas in the scalp along with occipital and cervical lymphadenopathy suggest possible pediculosis infestation.

Differential Diagnosis & Pitfalls

The scales of seborrheic dermatitis may be mistaken for pediculosis capitis; however, these scales are greasy, yellow, irregular in shape, and are easily removable, unlike the scales of pediculosis capitis, which adhere to the hair shaft.

Tinea capitis has similar pruritus and lymphadenopathy but is associated with alopecia. Nits are not found on close examination of the hair.

Psocid lice living off plant detritus may be found in the scalp of a child who plays in wooded areas but are morphologically distinct from Pediculosis humanis capitis.

Psoriasis, lichen planopilaris, and folliculitis all cause pruritic scalp but are morphologically distinctive skin disorders.

Best Tests

Demonstration of lice or nits on hair visually or under microscope.

Management Pearls

There is evidence of increasing resistance of lice to treatment with permethrin. If there is no response with permethrin, use an alternative therapy.

All household contacts should be examined and treated concurrently.

On the day of treatment, clothing worn that day and bed linens can be machine washed or dry cleaned to decrease the risk of fomite transmission.

Many "resistant" infestations are due to improper use of pediculicides or misdiagnosis of active infestations. After treatment, only individuals found to have living lice (move extremities when stimulated) should be considered to have an active infestation. Read all product labels for over-the-counter topical pediculicides and use exactly as directed by the manufacturer.

Therapy

Multiple topical and oral therapies are available for pediculosis. Prescription products should be reserved for patients with proven infestations that do not respond to proper application of over-the-counter pediculicides. Manual nit removal may be used as an adjuvant to topical therapy. Most herbal and home remedies are unproven in effectiveness and safety.

Over-the-Counter Pediculicides:

Permethrin 1% (Nix®): Apply to dry hair and rinse after 10 minutes. Repeat in 1–2 weeks.
Pyrethrins with piperonyl butoxide (RID®, Pronto®): Apply to dry hair and rinse after 10 minutes. Repeat in 1–2 weeks.

Prescription Products:

Malathion 0.5% lotion (Ovide®): Apply to dry hair and rinse after 8–12 hours. A repeat application is recommended after 1–2 weeks. Not indicated in children aged younger than 6 years.
Permethrin 5% (Elimite®): Apply to dry hair and rinse after 8–12 hours. Repeat in 1–2 weeks. Not indicated in infants aged younger than 2 months.
Oral ivermectin: 200 micrograms/kg in one oral dose. Repeat in 7–10 days. Not indicated in children aged younger than 5 years or weighing less than 15 kg.
Lindane, DDT, and carbaryl: Use of these products is rarely recommended due to potential systemic toxicity and limited effectiveness.

References

Meinking TL, Burkhart CN, Elgart G. Infestations. In: Bolognia J, Jorizzo JL, Rapini RP, eds. Dermatology. 2nd ed. St. Louis, MO: Mosby/Elsevier; 2008:1295-1297.

Tebruegge M, Runnacles J. Is wet combing effective in children with pediculosis capitis infestation?. Arch Dis Child. 2007 Sep;92(9):818-20. PubMed Id: 17715448

Goates BM, Atkin JS, Wilding KG, Birch KG, Cottam MR, Bush SE, Clayton DH. An effective nonchemical treatment for head lice: a lot of hot air. Pediatrics. 2006 Nov;118(5):1962-70. PubMed Id: 17079567

Leung AK, Fong JH, Pinto-Rojas A. Pediculosis capitis. J Pediatr Health Care. 2005 Nov-Dec;19(6):369-73. PubMed Id: 16286223

Meinking TL. Clinical update on resistance and treatment of Pediculosis capitis. Am J Manag Care. 2004 Sep;10(9 Suppl):S264-8. PubMed Id: 15515630

Yoon KS, Gao JR, Lee SH, Clark JM, Brown L, Taplin D. Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Arch Dermatol. 2003 Aug;139(8):994-1000. PubMed Id: 12925385

Jones KN, English JC. Review of common therapeutic options in the United States for the treatment of pediculosis capitis. Clin Infect Dis. 2003 Jun 1;36(11):1355-61. PubMed Id: 12766828

Chosidow O. Scabies and pediculosis. Lancet. 2000 Mar 4;355(9206):819-26. PubMed Id: 10711939

Associated Findings

Appearance
No Acute Distress

Body Location
Eyelids
Frontal Scalp
Occipital Scalp
Parietal Scalp
Post Auricular Scalp
Posterior Neck
Scalp
Temporal Scalp
Vertex Scalp

Distribution
Bilateral

Lesion
Concretions on Hair
Crust
Fine Scaly Papule

Signs and Symptoms
No Fever (Afebrile, Apyrexial)
Pruritus (Itching)

Social History
Day Care
Elementary School (K-5)
Homeless
Middle/High School (6-12)

Temporal
Developed Acutely Over Days to Weeks
Developed Steadily Over Weeks to Months